For two particles A and B moving along one straight line, which statements are always correct?

Select all that apply

• Option A

  If $x_A-x_B=0,$ they are at the same position

• Option B

  If $v_A-v_B=0,$ their separation has zero instantaneous rate of change

• Option C

  If $a_A-a_B=0,$ relative velocity is constant

• Option D

  If $v_A-v_B=0$ at one instant, they must collide at that instant